Researchers in the United States have found a significant connection between the use of air conditioning and a reduction in deaths caused by extreme heat, according to a study published in the journal Nature Health on August 31. The research, led by a team from the Yale School of Public Health, shows that air conditioning can lower the relative risk of mortality linked to heatwaves by about 57%. Using data from the U.S., the study estimates that residential air conditioning prevents more than 5,250 deaths annually. The researchers discovered that using air conditioning moderately is enough to achieve its protective benefits. Once a comfortable temperature is reached, further cooling does not provide additional health benefits. In fact, setting the air conditioner to very low temperatures may be unnecessary and could increase energy use. The health advantages include reducing strain on the cardiovascular system and preventing severe dehydration, which can lower the risk of strokes and heart failure. However, the study also raises important environmental concerns. Cooling systems account for about 10% of the world’s electricity use, contributing to roughly 1.13 billion tons of carbon dioxide emissions annually. As global temperatures rise, the growing number of air conditioning units is increasing the production of hydrofluorocarbons (HFCs), potent greenhouse gases with a warming effect much stronger than that of carbon dioxide. While air conditioning offers clear health benefits, the researchers caution that simply increasing access to air conditioners could lead to higher energy use and environmental harm. Additionally, not all households can afford to use air conditioning regularly, as more than a quarter of U.S. households face energy insecurity and may avoid using their units to save on electricity costs. Widespread adoption of air conditioners without addressing energy consumption could worsen the urban heat island effect and accelerate global warming. The study highlights the need for air conditioning but also stresses the importance of developing more sustainable cooling solutions.